this will be part of the next Yusynth project. But now I'll have enough to do to finish the other yusynths..

I'm very happy about the CV Resonance!!

I like to use the Envelope that is assigned to the CVFreq also to the Reso but negated. This gives a nice movement into the sound because the sharp hights can be nicely warm that way. Also with minimal attack times a beautiful Click can be generated...

Thank you for Yusynth! For me this is the perfect start in DIY and slowly I begin to uncover the mysteries of SDIY.

When Im done with the first modules Ill take some pictures for you to enjoy! But it could last a while until then because music making is still my main objective.

Thanks for posting this. I like the resonance control circuit. One question: why couple the audio through R37, R38 and C13 into the CV path that controls Q12?

This is the original resonance design by EMS . It is meant to linearize the response of the FET transistor and reduce distorsion, just as it is done in FET based phasers where a part of the audio is fed to the FET grid trough a capacitor. Osamu Hoshuyama has a page where he tested different feedback technique :
http://www5b.biglobe.ne.jp/~houshu/synth/PhaseFet0205.GIF

Dave Manley wrote:

Also, how much does the discrete opamp (Q7-Q11 and associated components) contribute to the character of the filter?

One may substitute a high impedance input integrated OPA to the discrete opamp (Q7-Q11). This would work and this is what is done on all the published so-called EMS clone schematics one can find on the net. I think that chances are that both versions distort/saturate differently. I have not tested it. My aim was to keep as close as possible to the original EMS design and sound._________________Yves

Yves, does this clone exhibit the pre or post '74 sound? (ie have you managed to capture that watery-ness that the original synthi VCS3 was so famous for? (listen to ¨early in the morning¨ by Kraftwerk some time if you don't know what I mean- those lovely 'bubbling mud' sounds )

Yves, does this clone exhibit the pre or post '74 sound? (ie have you managed to capture that watery-ness that the original synthi VCS3 was so famous for? (listen to ¨early in the morning¨ by Kraftwerk some time if you don't know what I mean- those lovely 'bubbling mud' sounds )

PS- any plans to clone the EMS Trapezoid Generator too?

I don't know what you mean and I haven't got the album you refer to. What I did is simply reproducing the EMS filter core, but with different trannies, I doubt that the sound is similar to very early models...

What made the Synthi filter so famous was its ability to make 'bubble-like' noises. It was something about a voltage lag on the input that made the sound. I don't think it can be reproduced with a normal lag processor. You are more likely though to get a similar effect (perhaps?) with a vactrol, although I think it was a simple capacitor in line with the CV input, that produced this unique response._________________ACHTUNG!
ALLES TURISTEN UND NONTEKNISCHEN LOOKENPEEPERS!
DAS KOMPUTERMASCHINE IST NICHT FÜR DER GEFINGERPOKEN UND MITTENGRABEN! ODERWISE IST EASY TO SCHNAPPEN DER SPRINGENWERK, BLOWENFUSEN UND POPPENCORKEN MIT SPITZENSPARKSEN.
IST NICHT FÜR GEWERKEN BEI DUMMKOPFEN. DER RUBBERNECKEN SIGHTSEEREN KEEPEN DAS COTTONPICKEN HÄNDER IN DAS POCKETS MUSS.
ZO RELAXEN UND WATSCHEN DER BLINKENLICHTEN.

Was that translated as "early in the morning"? No wonder I didn't recognize it either. I only have the original German version where it's called Morgenspaziergang, which would more correctly translate as "morning stroll".

More on topic: I guess a 15uF would be a better alternative for the 16uF than the 22uF? 15uF appears to be quite common over here.
Also, is a polarized one needed by the circuit, otherwise one could probably put in two 33uF in series to get a non-polarized 16.5uF.

Secomd, how important is the Hfe of the BC557? I checked mine, but all 50+ of them are BC557B. If the C is important, I need to get some new ones..._________________http://www.casia.org/modular/

More on topic: I guess a 15uF would be a better alternative for the 16uF than the 22uF? 15uF appears to be quite common over here.
Also, is a polarized one needed by the circuit, otherwise one could probably put in two 33uF in series to get a non-polarized 16.5uF.

This cap is just an audio decoupling cap between the filter and the output buffer. Changing from 16uF to 22uF just slightly extends the bandwith to low frequency, therefore 15uF,16uF or 22uF doesn't make a significant change here.

Etaoin wrote:

Second, how important is the Hfe of the BC557? I checked mine, but all 50+ of them are BC557B. If the C is important, I need to get some new ones...

I have no idea, I picked a BC557C because it was what I had at hand. I suppose it might change a bit the frequency range control but this can be adjusted by trimmer A1 and A2._________________Yves

OK I checked the bubbly stuff in Autobahn and I understand what you mean.
I also checked the various EMS schematics I have and apparently I have two versions, one is a polarized cap connected to the base of Q4 (first transistor of the expo converter) which I considered as a design mistake and a second version where the very same cap is connected between the negative rail and ground which makes sense indeed. In my "clone" I suppressed this cap.
If you want to recreate this bug/feature of the old version you will have to add a 10uF cap between the base of Q4 and the 0V level._________________Yves

Was that translated as "early in the morning"? No wonder I didn't recognize it either. I only have the original German version where it's called Morgenspaziergang, which would more correctly translate as "morning stroll".

As most Kraftwerk albums appear in two, three, or even four languages, I honestly thought it meant there was an English release that used that title. I wasn't critizing anyone's translation, just remarking I hadn't realized it was the same track because of the difference in title _________________http://www.casia.org/modular/

This might actually be the first module from your collection I'm having a bit of trouble with. The filter works fine, but I only have a bit of resonance if I turn the res pot fully CW and put a large CV into the red mod input. With large enough CV, the res pot works as expected, with no CV, the res pot doesn't do anything. I'm usually reasonably good at debugging, but I can't find anything obviously wrong._________________http://www.casia.org/modular/

Questions which version are you using ?
If using the discrete one are you using the C brand for the transistor ?
Have you tried different 2N3819 for the Q12, did you connect C14 the right way ? The FET (2N3819) is to be selected, a BF245 would not work (I know it because in my first design I used a BF245 without success), therefore try various 2N3819 to find the one that gives you the best range.

By the way a simple test for the resonance : simply disconnect C14, there the filter should wistle like a bird ! If this work, then check C14 and Q12.Last edited by yusynth on Sun Mar 16, 2008 12:25 pm; edited 1 time in total

I did some further testing and found that I need at least 5V at the resonance mod input (both pots fully CW) for it to oscillate and the res pot to work as expected.

I also tried removing R45 to see if U1b was doing odd things, but no luck. C13 is okay, so there isn't any current flowing to ground that way.

One thing I did notice was that when I connect my DWM to the gate of the FET and have the res pot fully CW, I first see -3V (as expected from the 680k/220k divider?) but that changes to -1.3V almost straight away. But maybe that's just caused by the DVM itself?

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